Large scale ozone generators (producing over 5 g/hr) generally have the humidity in the feed gas removed by air dryers and the excess heat generated from the corona discharge removed with a liquid cooling system.
All small ozone generators heretofore known, however, due to economical considerations must be able to function without air dryers and temperature controls and therefore suffer from a number of disadvantages:
(a) In generators producing small amounts of zone in relation to the cooling surfaces, little heat build up is realized and the relative humidity in the feed air obtained from most ambient conditions remains high. Consequently nitric acid will build up on the dielectric members. This has been a longfelt but usolved need in the industry.
(b) In all previous ozone generator designs the feed gas has been forced to travel the full length of the discharge gap between the electrodes. The characteristic oxidation time of nitrogen oxides and the consequent formation of nitric acid is approximately 10,000 times longer than that of ozone formation. This allows nitric acid sufficient time to form in the discharge gap.
(c) In all previous ozone generator designs the feed gas has been forced to travel the full length of the discharge gap between the electrodes. A certain percentage of ozone will then dissociate due to electron collisions and heat in the discharge gap.
(d) Contaminants from the feed gas will form a deposit on the surface area connecting the two counter electrodes and reduce the impedance of the generator and eventually load down the transformer below the corona inception voltage or if an insulating material which will form surface tracks is used, the insulator is usually destroyed.
(e) It is common in small ozone generators to use ceramic dielectric members that have various screen printed materials applied to them, which makes them costly to replace.
(f) Since untreated humid air is used, the generator will need periodic removal and cleaning. In most ozone generators this is a difficult process.
(g) It is common in small ozone generators to use the air flow from the distribution fan as a feed gas supply for the ozone generator, this causes the contaminants in the air to be deposited inside the generator and eventually cause it to fail.
(h) It is common in small ozone generators to expose the high voltage connector to the air flow from the distribution fan, this causes contaminants in the air to be deposited on the high voltage connector insulation material decreasing its impedance to ground potential and will eventually load down the high voltage transformer or if an insulating material which will form surface tracks is used, the insulator is usually destroyed.
(i) Small gas-tight ozone generators are commonly expensive to manufacture and difficult to disassemble for cleaning.